A memory element is known from DE 10 2009 023 153, in which a memory cell A having stable states A0 and A1 is connected in series to a memory cell B having stable states B0 and B1. In this memory element, state 0 can be coded in the combination of states A1 and B0, and state 1 can be coded in the combination of states A0 and B1. This memory element has high resistance, both in state 0 and in state 1, so that the element acts as a high-resistance resistor in each parasitic current path. These memory elements can be used to implement considerably larger storage matrices than with conventional memory cells.
The trade-off for this advantage is that, after reading out a state 1, the memory cell A is switched to state A1 and the memory cell B is switched to state B0, and the information written to the cells is thereby lost. The memory element does not automatically return from this state to the state that was present prior to the read-out. The read-out of state 1 is therefore destructive. So as to restore the original state, state 1 must again be written to the memory element.
Therefore, it is the object of the invention to provide a method by way of which memory elements of the type described in DE 10 2009 023 153 can be read out non-destructively. It is a further object of the invention to provide a memory element that is particularly suited for carrying out this method.
These objects are achieved according to the invention by a method according to the main claim and by a memory element according to the additional independent claim. Further advantageous embodiments will be apparent from the respective dependent claims.